Chat now with support
Chat with Support

syslog-ng Open Source Edition 3.24 - Administration Guide

Preface Introduction to syslog-ng The concepts of syslog-ng Installing syslog-ng The syslog-ng OSE quick-start guide The syslog-ng OSE configuration file source: Read, receive, and collect log messages
How sources work default-network-drivers: Receive and parse common syslog messages internal: Collecting internal messages file: Collecting messages from text files wildcard-file: Collecting messages from multiple text files linux-audit: Collecting messages from Linux audit logs network: Collecting messages using the RFC3164 protocol (network() driver) nodejs: Receiving JSON messages from nodejs applications mbox: Converting local email messages to log messages osquery: Collect and parse osquery result logs pipe: Collecting messages from named pipes pacct: Collecting process accounting logs on Linux program: Receiving messages from external applications python: writing server-style Python sources python-fetcher: writing fetcher-style Python sources snmptrap: Read Net-SNMP traps sun-streams: Collecting messages on Sun Solaris syslog: Collecting messages using the IETF syslog protocol (syslog() driver) system: Collecting the system-specific log messages of a platform systemd-journal: Collecting messages from the systemd-journal system log storage systemd-syslog: Collecting systemd messages using a socket tcp, tcp6, udp, udp6: Collecting messages from remote hosts using the BSD syslog protocol— OBSOLETE unix-stream, unix-dgram: Collecting messages from UNIX domain sockets stdin: Collecting messages from the standard input stream
destination: Forward, send, and store log messages
amqp: Publishing messages using AMQP collectd: sending metrics to collectd elasticsearch2: Sending messages directly to Elasticsearch version 2.0 or higher (DEPRECATED) elasticsearch-http: Sending messages to Elasticsearch HTTP Bulk API file: Storing messages in plain-text files graphite: Sending metrics to Graphite Sending logs to Graylog hdfs: Storing messages on the Hadoop Distributed File System (HDFS) Posting messages over HTTP http: Posting messages over HTTP without Java kafka: Publishing messages to Apache Kafka (Java implementation) kafka: Publishing messages to Apache Kafka (C implementation, using the librdkafka client) loggly: Using Loggly logmatic: Using Logmatic.io mongodb: Storing messages in a MongoDB database network: Sending messages to a remote log server using the RFC3164 protocol (network() driver) osquery: Sending log messages to osquery's syslog table pipe: Sending messages to named pipes program: Sending messages to external applications pseudofile() python: writing custom Python destinations redis: Storing name-value pairs in Redis riemann: Monitoring your data with Riemann slack: Sending alerts and notifications to a Slack channel smtp: Generating SMTP messages (email) from logs snmp: Sending SNMP traps Splunk: Sending log messages to Splunk sql: Storing messages in an SQL database stomp: Publishing messages using STOMP syslog: Sending messages to a remote logserver using the IETF-syslog protocol syslog-ng(): Forward logs to another syslog-ng node tcp, tcp6, udp, udp6: Sending messages to a remote log server using the legacy BSD-syslog protocol (tcp(), udp() drivers) Telegram: Sending messages to Telegram unix-stream, unix-dgram: Sending messages to UNIX domain sockets usertty: Sending messages to a user terminal: usertty() destination Write your own custom destination in Java or Python Client-side failover
log: Filter and route log messages using log paths, flags, and filters Global options of syslog-ng OSE TLS-encrypted message transfer template and rewrite: Format, modify, and manipulate log messages parser: Parse and segment structured messages db-parser: Process message content with a pattern database (patterndb) Correlating log messages Enriching log messages with external data Statistics of syslog-ng Multithreading and scaling in syslog-ng OSE Troubleshooting syslog-ng Best practices and examples The syslog-ng manual pages Creative Commons Attribution Non-commercial No Derivatives (by-nc-nd) License Glossary

The flags() options of regular expressions

Similarly to the type() options, the flags() options are also optional within regular expressions.

The following list describes each type() option's flags() options.

PCRE

Starting with syslog-ng OSE version 3.1, PCRE expressions are supported on every platform. If the type() parameter is not specified, syslog-ng uses PCRE regular expressions by default.

PCRE-style regular expressions have the following flags() options:

disable-jit:

Switches off the just-in-time compilation function for PCRE regular expressions.

global:

Usable only in rewrite rules: match for every occurrence of the expression, not only the first one.

ignore-case:

Disable case-sensitivity.

newline:

When set, it changes the newline definition used in PCRE regular expressions to accept either of the following:

  • a single carriage-return
  • linefeed
  • the sequence carriage-return and linefeed ('\r', '\n' and '\r\n', respectively)

This newline definition is used when the circumflex and dollar patterns ('^' and '$') are matched against an input. By default, PCRE interprets the linefeed character as indicating the end of a line. It does not affect the '\r', '\n' or '\R' characters used in patterns.

store-matches:

Store the matches of the regular expression into the $0, ... $255 variables. The $0 stores the entire match, $1 is the first group of the match (parentheses), and so on. Named matches (also called named subpatterns), for example, (?<name>...), are stored as well. Matches from the last filter expression can be referenced in regular expressions.

unicode:

Use Unicode support for UTF-8 matches: UTF-8 character sequences are handled as single characters.

utf8:

An alias for the unicode flag.

Example: Using PCRE regular expressions
rewrite r_rewrite_subst {
    subst("a*", "?", value("MESSAGE") flags("utf8" "global"));  
};
Literal string searches

Literal string searches have the following flags() options:

global:

Usable only in rewrite rules: match for every occurrence of the expression, not only the first one.

ignore-case:

Disable case-sensitivity.

store-matches:

Store the matches of the regular expression into the $0, ... $255 variables. The $0 stores the entire match, $1 is the first group of the match (parentheses), and so on. Named matches (also called named subpatterns), for example, (?<name>...), are stored as well. Matches from the last filter expression can be referenced in regular expressions.

substring:

During the matching process, patterns (also called search expressions) are matched against the input string starting from the beginning of the input string, and the input string is matched only for the maximum character length of the pattern. The initial characters of the pattern and the input string must be identical in the exact same order, and the pattern's length is definitive for the matching process (that is, if the pattern is longer than the input string, the match will fail).

Example: matching / non-matching patterns for the input string 'exam'
For the input string 'exam',
  • the following patterns will match:
    • 'ex' (the pattern contains the initial characters of the input string in the exact same order)
    • 'exam' (the pattern is an exact match for the input string)
  • the following patterns will not match:
    • 'example' (the pattern is longer than the input string)
    • 'hexameter' (the pattern's initial characters do not match the input string's characters in the exact same order, and the pattern is longer than the input string)
prefix:

The given literal string will match when the pattern is found within the input. Unlike in the case of the substring flags() option, the pattern does not have to be identical with the given literal string.

Glob patterns without regular expression support

There are no supported flags() options for glob patterns without regular expression support.

Perl Compatible Regular Expressions (PCRE)

Starting with syslog-ng OSE version 3.1, PCRE expressions are supported on every platform. If the type() parameter is not specified, syslog-ng OSE uses PCRE regular expressions by default.

The following example shows the structure of PCRE-style regular expressions in use.

Example: Using PCRE regular expressions
rewrite r_rewrite_subst {
    subst("a*", "?", value("MESSAGE") flags("utf8" "global"));  
};

PCRE-style regular expressions have the following flags() options:

disable-jit

Switches off the just-in-time compilation function for PCRE regular expressions.

(missing or bad snippet)(missing or bad snippet)
newline

When configured, it changes the newline definition used in PCRE regular expressions to accept either of the following:

  • a single carriage-return
  • linefeed
  • the sequence carriage-return and linefeed (\r, \n and \r\n, respectively)

This newline definition is used when the circumflex and dollar patterns (^ and $) are matched against an input. By default, PCRE interprets the linefeed character as indicating the end of a line. It does not affect the \r, \n or \R characters used in patterns.

(missing or bad snippet)
unicode

Uses Unicode support for UTF-8 matches: UTF-8 character sequences are handled as single characters.

utf8

An alias for the unicode flag.

Literal string searches

Literal string searches have the following flags() options:

(missing or bad snippet)(missing or bad snippet)
prefix:

During the matching process, patterns (also called search expressions) are matched against the input string starting from the beginning of the input string, and the input string is matched only for the maximum character length of the pattern. The initial characters of the pattern and the input string must be identical in the exact same order, and the pattern's length is definitive for the matching process (that is, if the pattern is longer than the input string, the match will fail).

Example: matching / non-matching patterns for the input string 'exam'
For the input string 'exam',
  • the following patterns will match:
    • 'ex' (the pattern contains the initial characters of the input string in the exact same order)
    • 'exam' (the pattern is an exact match for the input string)
  • the following patterns will not match:
    • 'example' (the pattern is longer than the input string)
    • 'hexameter' (the pattern's initial characters do not match the input string's characters in the exact same order, and the pattern is longer than the input string)
(missing or bad snippet)
substring:

The given literal string will match when the pattern is found within the input. Unlike flags("prefix"), the pattern does not have to be identical with the given literal string.

Glob patterns without regular expression support

There are no supported flags() options for glob patterns without regular expression support.

Related Documents

The document was helpful.

Select Rating

I easily found the information I needed.

Select Rating